In the boating industry it is desirable to be able to measure the speed of a boat as it travels through water. Increasingly water patrols are regulating speed of boat traffic and yet for many boat operators there is no reliable way to measure speed. A number of prior art solutions have been developed to measure boat speed in water.
One common approach to measuring speed is to use a system with a small propeller or wheel that turns faster as the boat travels faster through the water. These systems are unreliable primarily because of debris in the water and problems associated with a system having moving parts exposed to the hydrodynamic forces that can be generated by boats traveling over 25 miles per hour in the water.
Another common approach to measure speed is to use a pressure sensing tube with an opening in the direction of boat travel. Static pressure builds up in the tube as the boat speed increases. The pressure is read out by a gauge or other device that converts the pressure into a visual display indicative of boat speed. One problem with these sensing tube devices has been air trapped in the tube which is used to transfer pressure. Pressurized air trapped in the tube of the speedometer will give erratic and false readings because of the compressibility of the trapped air. Another problem with these pressurized tubes is in the device used to read out a speed. Often times a needle gauge is placed on the end of the line. This is a simple arrangement but yields a device that is difficult to read and that is subject to vibration induced needle bounce and damage due to vibration present on a small boat. These sensing tube systems also have problems with the depth of the probe, which needs to be out of turbulent flow. There is also a problem with snagging debris such as sticks in the water which can break off the tube.
The present invention relates to a boat mounted speedometer that solves the problems of prior approaches. The current system provides an economical system that generates a quick, reliable readout of speed to a boat operator.
The present invention provides a water filled probe having the ability to automatically bleed off trapped air so as to provide a reliable speed signal at all times. Further the present system provides a probe that can flex out of the way of debris such as sticks and water plants. The system further provides a back lit digital display that gives an easily read indication of boat speed at all times including at night.
The present invention provides an easy to install automatic air bleed using a simple plastic float.
These and other advantages of the present invention will become apparent from the detailed description of the invention.